Quote Originally Posted by Luin View Post
It'll also pick caster gear. I think it looks only at ilvl.
No, I think the "Recommended Gear" algorithm mainly looks at the primary stat for the class/job in question. Only if that is equal between gear pieces does it go on and consider other stats.
For tanks the primary stat is Vitality, so you will usually get recommended whatever gear item provides the most Vitality among those you can equip.